Stress auf allen Ebenen
Moleküle, Organismen,
Le e sge ei s hate
Fachbereich Biologie
15. Dezember 2014
Bioze tru Klei Flot ekOhnhorststraße 18
22609 Hamburg
Organisiert von den Studierenden des
Master-Studiengangs Biologie
Tagungsband
Einleitung
„Stress auf allen Ebenen - Moleküle, Organismen, Lebensge-
meinschaften“
Das Wort „Stress“ werden die Meisten mit persönlichen Erfahrun-
gen aus Beruf, Studium und Alltag verknüpfen. Doch Stress ist in der
Biologie viel mehr als eine negative Erfahrung - es ist ein Motor der
Evolution. Der Einluss von Stress lässt sich bei Individuen und Le-
bensgemeinschaften beobachten und ist bis auf die Ebene von Zellen
und Molekülen zu erkennen. Dabei stellt sich die Frage, was bedeutet
Stress auf unterschiedlichen Ebenen eigentlich? Und welche Reaktio-
nen ruft Stress hervor? Aktuelle Forschungsprojekte und -ergebnisse
zu diesem Thema sollen auf der Tagung des Fachbereichs Biologie
vorgestellt und diskutiert werden.
Wir, Studierende des Masterstudiengangs Biologie wünschen Ihnen
eine erfolgreich Tagung mit interessanten Gesprächen und Anregun-
gen für neue Ideen und Kooperationen.
Die Organisation:
Die Tagung wird im Rahmen einer Lehrveranstaltung von den Studie-
renden des Master of Science Biologie organisiert.
Durch „problemorientiertes Lernen“ sollen die Studierenden nach
Abschluss der Veranstaltung das Wissen haben eine Tagung zu or-
ganisieren und durchzuführen. Was ist projektorientiertes Lernen?
Projektarbeit (auch oft als Zukunftswerkstatt bezeichnet) ist das
selbstständige Bearbeiten einer Aufgabe oder eines Problems durch
eine Gruppe von der Planung über die Durchführung bis zur Präsen-
tation des Ergebnisses. Projektarbeit ist eine Methode demokrati-
schen und handlungsorientierten Lernens, bei der sich Lernende zur
Bearbeitung einer Aufgabe oder eines Problems zusammeninden,
um in größtmöglicher Eigenverantwortung immer auch handelnd ler-
nend tätig zu sein, eingefahrene Gleise verlassen und Ideen für Neues
entwickeln.
Einleitung
Wir danken unseren Unterstützern:
Analytik Jena AG
Biomol GmbH
Biozym Scientiic GmbH
Eppendorf AG
Peter Kölln KGaA
Carl Roth GmbH + Co. KG
Sarstedt AG + Co.
VWR International GmbH
Nur Hier GmbH
Nikon GmbH
Stern & Schatz GmbH
Man kann Projektunterricht bezeichnen als “ganzheitliche, integrative
Lernform“, der ein Höchstmaß an curricularer Ofenheit zukommt und
die den bestmöglichen Raum für Lernendenmitbestimmung und
-orientierung bereitstellt.
So sieht der Unterricht in Projektphasen aus:
http://www.hd-mint.de/lehrkonzepte/lehrkonzepte/projektarbeit/
Vorträge
in chronologischer
Reihenfolge
Vorträge
Prof. jun. Dr. Mirjam Perner [email protected] AG Molekularbiologie mirkobieller Konsortien
“Gestresste“ Mikroben in extremen Habitaten
Mikroben besiedeln nahezu jeden Lebensraum auf unserem Plane-
ten. Man indet sie von der Atmosphäre bis in die Tiefsee und sogar
in Gesteinen tief unter dem Meeresboden. Einige sind optimal an
außergewöhnliche oder radikale Bedingungen, die in extremen Hab-
itaten vorherrschen können, adaptiert. So existieren unterschiedliche
Mikroben in bspw. jeweils besonders heißen, kalten oder aus unserer
Perspektive toxischen Habitaten. Hier lege ich den Fokus auf den
Stress, dem verschiedene Mikroben, die hydrothermale Tiefseequel-
len besiedeln, ausgesetzt sind: In hydrothermalen Tiefseesystemen
herrschen bspw. besonders hohe Temperaturen, Sauerstof kann
mitunter gar nicht vorhanden sein, und toxische Substanzen, wie z.B.
Schwermetalle, können in sehr hohen Konzentrationen vorliegen.
Prof. Dr. Arp Schnittger
Reaktionen der Planzen nach DNA-Schäden
Vorträge
Dr. Jens Oldeland [email protected] AG Jürgens (BEE)
Some like it hot: Stress in Wüstenrändern
Wüsten gelten allgemein als Ökosysteme mit einem hohem Stressfak-
tor. Organismen die in Wüsten überleben haben sich an die harschen
klimatischen und edaphischen Bedingungen angepasst. Der allge-
genwärtige Klimawandel droht die Wüstenränder weltweit auszudeh-
nen und die Verbreitungsgrenzen von Organismen zu verschieben.
Wüstenränder sind die Ökotonbereiche zwischen ariden Wüsten und
semi-ariden Grasländern bzw. Steppen. In Ökotonen lassen sich Ef-
fekte von Stress auf die ökologische Nische einzelner Arten sowie auf
die Artenzusammensetzung in Planzengesellschaften besonders gut
analysieren. Wir haben einen Datensatz zusammengetragen der di-
verse Planzengesellschaften in Wüstenrändern und die dort vorherr-
schenden klimatischen Bedingungen umfasst. Diese Daten stammen
aus den Wüsten Nord- und Südafrikas. Wir verwenden multivariate
Gradientenanalyse und hierarchische Generalisierte Modelle, soge-
nannte HOF-Modelle, zur Charakterisierung der Art-Antwort Kurven
auf verschiedene Stressgradienten, z.b. Maximal-Temperatur, jährliche
Niederschlagsmenge etc. Wir identiizieren damit eindeutige hitzeto-
lerante Arten und quantiizieren deren ökologische Nische, weiterhin
betrachten wir die Konsequenzen für die Artenzusammensetzung
der Planzengesellschaften und deren Resilienz in den betrachteten
Wüstenrändern.
Vorträge
Safaa Dalla [email protected] AG Molekulare Evolutionsbiologie
Four mutations in the target site for cardenolides explain the
insensitivity of Oncopeltus fasciatus to highly toxic plant
chemical defenses
Intricate adaptations of herbivorous insects to plant chemical defen-
ses are widespread. Understanding the genetic basis of these adapta-
tions is a central question in chemical ecology. Oncopeltus fasciatus,
the large milkweed bug, is specialized on plants producing toxic se-
condary compounds called cardenolides which are speciic inhibitors
of the Na,K-ATPase. Genetic analyses indicate that O. fasciatus pos-
sesses three gene copies bearing diferent amino acid substitutions
in the cardenolide target site. We expressed the cardenolide sensitive
Na,K-ATPase α-subunit of Drosophila melanogaster in combination
with diferent β-subunits in baculovirus-infected Sf9 cells and intro-
duced the amino acid substitutions observed in the diferent ATPase
α-copies of O. fasciatus. To determine the functional importance of
the introduced substitutions, the sensitivity of the ATPase activity to
increasing cardenolide concentrations was measured and compared
to that of nervous tissue of O. fasciatus which was highly insensitive
to the cardenolide. The substitutions signiicantly decreased Na,K-AT-
Pase sensitivity to cardenolide in a stepwise manner. The combined
substitutions at four positions closely mimicked the behavior of the
Na,K-ATPase of nervous tissue. They thus appear to be responsible for
the pronounced insensitivity of O. fasciatus to cardenolides and are
central for the adaptation to its host plant’s chemical defenses.
Vorträge
Dr. Renja Romey-Glüsing [email protected] AG molekulare Evolutionsbiologie
How to reduce stress with toxic food – The Senecionine Mo-
nooxygenase of Longitarsus jacobaeae
The lea beetle Longitarsus jacobaeae is one of very few animals that
are specialized on tansy ragwort (Senecio jacobaea). This common
wild lower is known to be highly toxic, not only for insects but also
for cattle and horses due to its content in pyrrolizidine alkaloids,
mainly senecionine-N-oxide. This compound serves (the plant) as
defense mechanism against herbivores and is responsible for hepato-
toxic or even lethal efects for farm animals.
In this study we investigated which physiological adaptions allow
Longitarsus jacobaeae to feed unharmed on Senecio jacobaea. The
challenge in dealing with pyrrolizidine alkaloids consists in their
conversion from N-oxides into tertiary alkaloids in the herbivores’ gut
which then bring about the toxic efects. We identiied sequences
in the beetle’s transcriptome that are similar to known lavin-mo-
nooxygenases. Based on this information we were able to express
and harvest the recombinant protein in Sf9 cells. Activity tests with
tertiary senecionine demonstrated that the lea beetle has a senecio-
nine-monooxygenase able to speciically convert tertiary senecionine
into the harmless N-oxide and furthermore that this enzyme is more
active than the previously described enzyme of the arctiid moth Tyria
jacobaeae. The main tissue for this metabolization could be identiied
by quantitative real-time PCR.
Vorträge
Dr. Stefanie Nolte [email protected] AG Angewandte Planzenökologie
Beweidung – Stress und Möglichkeit
Beweidung bedeutet für Planzen Stress durch Verlust von Biomasse
und durch Bodenverdichtung. Doch während einige Arten diesen
Stress nicht überstehen, gibt es andere die ihn nutzen.
Ole [email protected] Tierökologie & Naturschutz
Thermal limits of lizards along a steep environmental gradient
Temperature is a crucial aspect in reptile’s biology and most species
attempt to reach and maintain a certain target body temperature
(Tpref
) that allows optimal performance. Body temperature below
Tpref
result in poor performance and higher temperature lead to heat
stress and overheating. However, “cold blooded” animals are only
able to achieve body temperatures within the operative environmen-
tal temperature range. Temperature preferences of the animals and
the potential to compensate temperature luctuations behaviorally
or physiologically could predict the distribution of species but also
the extinction risk in the face of climate warming. We investigated
the thermal ecology of three Malagasy lizard species in their natural
habitat along a steep environmental gradient to ind out whether the
animal’s distribution is restricted by the thermal regime. Our indings
show that all species show high behavioral lexibility but only little
physiological adaptation and the distribution of the species is mainly
limited by the environmental temperature.
Vorträge
Prof. Dr. Christian Voigt [email protected] AG Phytopathologie und Biochemie
Stress - Wie sich die Planze wehrt
Planzen sind ständig physikalischem, chemischem und biologi-
schem Stress ausgesetzt. Gegen diesen wehrt sich die Planze durch
Zellwandverstärkungen. Super-Resolution-Mikroskopie erlaubt nun
einen Einblick in deren Struktur.
Bianca Wist & Janina [email protected] Tierökologie & Naturschutz
Energetics of Lepilemur leucopus
Lepilemur leucopus is present in the dry deciduous and xerophytic
spiny forest of southern Madagascar. The climate is characterized by
hot wet summers, with temperatures above 40°C and cold dry win-
ters, with temperatures below 10°C at night, due to / through climate
change the greatest warming and decreases in rainfall are expected
in this region. Using indirect calometry with portable analyzers fol-
lowing standard techniques we measured the resting metabolic rate
(RMR) of Lepilemur leucopus under diferent ambient temperatures in
the wet and dry season. We deined the “thermal neutral zone” (equi-
librium between heat production and heat loss) of this species bet-
ween an ambient temperature of 25-30°C, below and after that the
animals have to produce heat or cool down. Due to climate change,
regional warming and decreases in rainfall could lead to huge heat
stress for Lepilemur leucopus.
Vorträge
Tanja Kotur [email protected] AG molekulare Planzenphysiologie
Cell Death Regulation in Plants
Cell death is important for plant growth and development. The Ara-
bidopisis thaliana SENESCENCE ASSOCIATED E3 UBIQUITIN LIGASE1
(SAUL1) is a member of the plant U-box armadillo repeat (PUB-ARM)
protein family and is an essential regulator of leaf senescence, cell de-
ath and immunity in plants. Mutant saul1 plants lacking expression of
the SAUL1 gene show early senescence and cell death in stress con-
ditions. In order to understand the SAUL1 signaling pathway and the
function of SAUL1 in cell death control, we performed a suppressor
screen with saul1 plants. We identiied 8 independent allelic suppres-
sors rescuing the saul1 phenotype. With the help of next generation
sequencing and map-based approaches we will identify diferent
suppressors that are part of the SAUL1 signaling network.
Vorträge
Dr. Jörg Bormann [email protected] AG Molekulare Phytopathologie und Genetik
Stress signaling cascades in Fusarium graminearum
The fungal pathogen Fusarium graminearum forms specialized
infection cushions (ICs) essential for penetration of wheat loral-leaf
cells. To understand the molecular basis of infection cushion develop-
ment, ICs and non-invasive runner hyphae (RH) were isolated by laser
capture microdissection (LCM) and separately subjected to RNAseq.
Quantitative expression analysis show marked diferences in gene
expression patterns between RH and ICs:
The majority of known and putative secondary metabolite gene clus-
ters, including those responsible for trichothecene and butenolide
production, are signiicantly up-regulated in ICs.
Carbohydrate-modifying enzymes (CAZymes) with proven capa-
cities for cell-wall degradation are exclusively present in ICs. In total,
174 genes encoding for CAZymes are diferentially expressed (42 in
RH, 132 in ICs).
Genes encoding for enzymes involved in reactive-oxygen species me-
tabolism reside in the upper ranks of diferentially expressed genes
(DEGs). Secreted ROS-related enzymes (SREs), presumably involved in
plant-defense response, are relatively enriched in ICs.
We identiied a large subset of transcripts encoding for putative
efector proteins.
By use of this novel transcriptional proiling of runner hyphae and
infection cushions from a fungal plant pathogen obtained under in
planta conditions, we gain new insights in the initial infection process
of F. graminearum on wheat. Complementary to this approach, fun-
ctional characterization of genes and histological analyses are ongo-
ing. First results will be presented.
In general, we conclude that infection cushions serve as an armory of
virulence factors, enabling the pathogen to enter the host.
Vorträge
Jonathan Bank [email protected] AG Herwig
Dealing with stress during winter - Inluence of thyroid hor-mones on metabolism and spontaneous daily torpor in the
Djungarian hamster
Djungarian hamsters (Phodopus sungorus) live in a seasonally chan-
ging environment. To cope with harsh winter conditions they un-
dergo multiple changes in behaviour and physiology including daily
torpor, a state of hypometabolism and hypothermia. The physiology
of these homeothermic animals is well adapted to survive hypother-
mia, however the driving mechanisms are not well understood. Thy-
roid hormones (TH) play a key role in regulation of seasonal as well
as acute changes in metabolism. In our study we investigated efects
of TH on the torpor response. TH levels were increased by giving T4,
T3 or decreased by methimazole via drinking water. Body tempera-
ture was recorded during the entire experiment and gene expression
was analysed by qPCR. High or low serum T3 levels had pronounced
reciprocal efects on torpor bout frequency and duration. Expression
of genes involved in T3 metabolism (dio2, dio3) indicated a tissue
speciic response to treatment. T
orpor per se afected dio2 and dio3 expression irrespective of treat-
ment or tissue, suggesting down regulation of T3 production during
hypometabolism. Uncoupling proteins, target genes of T3, were
afected by treatment as well as torpor. Understanding molecular
pathways inluenced by TH action will help to understand general
regulatory mechanisms of metabolism and body temperature.
Vorträge
Anika Glasenapp [email protected] AG Molekulare Phytopathologie
Fighting the Rivals - Secondary Metabolites as Bioactive
Compounds
For the successful infection of its host plant wheat, the phytopatho-
genic ascomycete Fusarium graminearum forms complex infection
structures like lobate appressoria and infection cushions. By the use
of a transcriptome sequencing approach of these structures, it was
found that the production of the secondary metabolites deoxyniva-
lenol (DON), butenolides and aurofusarin is drastically upregulated
during infection of wheat loret organs compared to epiphytically
growing hyphae. The lack of aurofusarin, DON, and butenolide bio-
synthesis does not compromise initial infection. However, it is assu-
med that these secondary metabolites are produced to act as bioac-
tive compounds. In vitro analyses showed that DON, aurofusarin, and
butenolides display antimicrobial and antifungal activity. Aurofusarin,
for example, inhibits growth of Bacillus subtilis and Candida albicans.
This bioactive function could prevent biotic stress for F. graminearum
caused by antagonistic
organisms. Our results provide novel insights in co-evolutionary as-
pects of pathogenic development and stress prevention.
Vorträge
Prof. Dr. horsten Burmester [email protected] AG Tierphysiologie
Sauerstoffversorgung und Sauerstoffmangel
bei Wirbeltieren
Um eine fortlaufende Energieproduktion sicherzustellen, haben Tiere
eine Reihe von Strategien zur verbesserten Sauerstofaufnahme und
–verteilung entwickelt. Dazu gehören unter anderem die respiratori-
schen Proteine, die bei den Wirbeltieren zur Familie der Globine ge-
hören. Hämoglobin und Myoglobin zählen dabei zu den bekanntes-
ten und am besten untersuchten Proteinen in der biomedizinischen
Forschung. Unsere Studien der letzten Jahre führten zur Entdeckung
von sechs weiteren Globintypen: Androglobin, Neuroglobin, Cytoglo-
bin, Globin E, Globin X und Globin Y. Die Untersuchung dieser "-
neuartigen" Globine zeigt eine spannende Evolutionsgeschich-
te dieser Proteine und breit gefächertes Funktionsspektrum, teilweise
jenseits der Sauerstofversorgung.
Eine Reduktion der zur Verfügung stehenden Sauerstofmenge kann
durch Umweltbedingungen oder Krankheiten verursacht werden.
Exemplarisch können anhand tauchender Säuger (Wale und Robben)
und verschiedenen Fischarten verschiedene Strategien aufgezeigt
werden, welche die Sauerstofversorgung verbessern, den Sauerstof-
verbrauch minimieren oder alternative Stofwechselwege nutzen.
Ein besonderer Fokus der vorgestellten Arbeiten liegt dabei auf dem
Gehirn, welches bei Wirbeltieren besonders sensitiv gegenüber Sau-
erstofmangel ist.
Vorträge
Michael Mentges [email protected] AG Molekulare Phytopathologie
Real-time monitoring of stress-induced hydrogen peroxide
production by Fusarium graminearum using the luorescent indicator protein “HyPer”
The plant pathogenic ascomycete Fusarium graminearum (teleo-
morph Gibberella zeae) is the main causal agent of the head blight
disease of wheat (Triticum aestivum L.). This leads to major economic
losses by accumulation of mycotoxins.
Reactive oxygen species (ROS), like hydrogen peroxide (H2O
2) and
superoxide anions, play an important role in the interaction between
the host plant and the fungus. They are used to induce oxidative
stress on both sides. The plant-derived ROS is supposed to inhibit
fungal growth inside the plant tissue, while F. graminearum as a
necrotrophic pathogen releases ROS in order to harm the host plant.
By use of a novel luorescent indicator protein for H2O
2, called HyPer,
we, for the irst time, established a technique to monitor H2O
2-dyna-
mics in fungal cells. In the presence of H2O
2, HyPer changes its con-
formation, leading to altered luorescence characteristics allowing
ratiometric readouts.
Analyses of HyPer-expressing strains of F. graminearum using luoro-
metry and confocal laser scanning microscopy revealed rapid luc-
tuations of intracellular H2O2-concentrations in response to various
stresses like oxidative, osmotic, and thermal stress. HyPer is, therefore,
an excellent tool for real-time ratiometric analyses of stress-induced
production of ROS.
Vorträge
Dr. Daniela Hirnet [email protected] AG Neurophysiologie
Role of adenosine in the processing of olfactory information
Stress is the response of an organism to unfavourable environmental
conditions and often leads to adjustment of physiological functions
or behaviour. The olfactory system is designed to analyse the animal´s
chemical surroundings and therefore is suitable for the perception
of a variety of stress-factors such as the odour of predators. Odours
are detected by olfactory sensory neurons in the nasal epithelium
which convey the information to the olfactory bulb (OB), the irst
relay station of the olfactory sensory pathway in the CNS. Although
animals dispose only a limited repertoire of odorant receptors in the
sensory neurons they are able to discriminate thousands of odours.
This is achieved by intense processing of the sensory information
by local neuronal circuits in the OB creating odour-speciic activity
patterns. We suggest that adenosine plays a role in the reinement of
these activity patterns. Adenosine is a ubiquitous neuromodulator,
involved in many physiological processes e.g. the induction of sleep.
In our everyday life we use the blockade of adenosine A1-receptors
by cafeine, an ingredient of cofee, to counteract the dampening
efect of adenosine on neuronal activity. In the OB adenosine reduces
background activity and therefore increases the signal to noise ration
of the odour signal.
Vorträge
Prof. Dr. Sigrun Reumann [email protected] AG Reumann
Die Funktion von NDR1-ähnlichen Proteinen in Peroxisomen und in der planzlichen Pathogenantwort
Nicht nur Tiere, sondern auch Planzen besitzen ein angeborenes Im-
munsystem. So sind Wildplanzen, im Gegensatz zu hoch gezüchte-
ten landwirtschaftlichen Kulturplanzen, in der Regel in der Lage, An-
grife durch Krankheitserreger erfolgreich abzuwehren. Peroxisomen
sind wie Mitochondrien und Chloroplasten ein essentielles Zellorga-
nell in nahezu allen höheren Organismen. Seit Kurzem ist bekannt,
dass Peroxisomen eine wichtige Rolle in der planzlichen Immunität
spielen. Durch bioinformatische Vorhersagen und experimentelle
Proteom-Analysen haben wir mehrere, bislang unbekannte Peroxiso-
menproteine in der Modellplanze Arabidopsis thaliana mit Ähnlich-
keit zu bereits charakterisierten Verteidigungsproteinen gefunden.
Interessanterweise wird die Steuerung einiger Verteidigungsproteine
zu Peroxisomen ofenbar durch alternatives Spleißen reguliert. Unter
den neu vorhergesagten Peroxisomen-Proteinen sind etliche Homo-
loge des prototypischen Abwehrproteins NDR1 (NON-RACE-SPECIFIC
DISEASE RESISTANCE 1). Die Zielsteuerung zu Peroxisomen wurde für
etliche Homologe in vivo nachgewiesen. Mit Hilfe von Expressions-
analyse, reverser Genetik, Modellierungsversuchen und Proteinkristal-
lisation versuchen wir momentan, die Funktion dieser Proteine in der
Pathogenantwort aufzuklären.
Vorträge
Jana [email protected] Tierökologie & Naturschutz
Effects of anthropogenic habitat fragmentation on different
aspects of amphibian diversity in Ranomafana rainforest,
Madagascar
Madagascar’s ecosystems are severely inluenced by anthropogenic habitat
alterations such as deforestation, degradation and fragmentation. Although
in general these disturbances of natural ecosystems are thought to have
negative efects on biodiversity, there is no consistent pattern on species’
and communities’ reactions and therefore, ecosystem consequences remain
poorly known. Usually, not all species react in the same way to disturban-
ces. Undisturbed forests outside protected areas are declining rapidly and
today’s protected areas might not be suicient to protect all extant species
in the long-term. For conservation planning it is hence important to under-
stand fragmentation efects on biodiversity and assess the diversity and
conservation value of disturbed habitats.
In a three-year study we determined diferent aspects of amphibian diversi-
ty along streams and in terrestrial forest parts, and analyzed diferences on
a gradient of three major habitat types: continuous forest (i.e., Ranomafana
National Park), forest fragments, and matrix (secondary vegetation, banana
plantations, rice ields). In general, fragmentation efects on diversity were
weak, i.e. there were no diferences in species richness between continuous
forest and fragments, but diferences in species composition. This indicates
that fragments represent suitable habitat for amphibians. Species richness
and composition in the matrix varied highly between diferent matrix types.
Streams in the matrix and banana plantations harboured as many species
as continuous forest and fragments, indicating that even highly altered
habitats can act as vital corridors and/or habitats for many species if at
least some habitat structures such as small gallery forests along streams are
maintained. However, diversity in secondary vegetation and rice ields was
signiicantly reduced.
We conclude that forest fragments and even some matrix habitats outside
protected areas are important refuges of amphibian diversity in Mada-
gascar, and should be included to a greater extent in conservation planning.
We discuss the exposure to high natural disturbances (e.g., cyclones) as a
factor that predisposes the exceptional resilience of Madagascan amphibi-
ans to anthropogenic disturbances.
Vorträge
PD Dr. Sabine LüthjeAG Lü[email protected]
Extremwetter, Stress für Planzen?
Der Klimawandel macht sich u.a. durch Häufung von Starkregen und
Trockenperioden bemerkbar. Wie reagieren Nutzplanzen auf kurz-
zeitige Überlutung? Welche molekularen Mechanismen werden
aktiviert?
Posterbeiträge
in alphabetischer
Reihenfolge
Michael Baum
Molekulare Evolutionsbiologie
Poison is a matter of perspective: The Lily of the valley
(Convallaria majalis) and the Onion Beetle (Lilioceris
merdigera, Chrysomelidae, Criocerinae)
Abstract:
Elected the „Poisonous Plant of the Year 2014“ in Germany,
the Lily of the valley Convallaria majalis owes its toxicity to
the production of cardenolides.
Cardenolides are able to inhibit the ubiquitous enzyme Na/K-
ATPase, which is found in the plasma membrane of all animal
cells. Nevertheless, larvae and imagines of Lilioceris
merdigera, often found on Allium sp., do feed on the leaves
of C. majalis.
After feeding on C. majalis for 5 days followed by Allium for 3
days, the defensive secretions of L. merdigera did not contain
any cardenolides and neither did the beetle itself. Sequence
analysis of the beetle Na/K-ATPase revealed none of the
mutations known to make the enzyme less sensitive to
cardenolides in other species. In tracer feeding experiments
with ³H-marked cardenolides, the bulk of radiation was
recovered from the beetle feces, indicating a protective
mechanism in the gut wall to prevent cardenolides from
entering the hemolymph.
Disposing cardenolides via feces may be advantageous to the
larvae of L. merdigera. They cover themselves with a fecal
shield, which often exceeds the size of the larvae itself. The
ability of the fecal shield to offer chemical protection was
assessed in a bio-assay with predatory ants.
Julia Berscheminski
Arbeitsgruppe Virale Transformation, Heinrich-Pette Institut,
Leibniz-Institut für Experimentelle Virologie
Sp100 isoform-specific regulation of human Adenovirus type
5 (Ad5) gene expression
Abstract:
PML-NBs (PML nuclear bodies) are multiprotein complexes
that have been implicated in a general antiviral defense based
on their capacity to recruit SUMOylated host restriction
factors upon interferon stimulation and stress. Paradoxically,
the genomes of various DNA viruses become associated with
PML-NBs, and initial sites of viral transcription/replication
centers are often juxtaposed to these domains. To ensure
efficient viral replication, restriction factors must be inhibited
by expressing viral early gene products that functionally limit
PML-NB-associated antiviral effects. To benefit from the co-
activating capabilities of Sp100A and simultanously prevent
transcriptional repression by Sp100B/C/HMG, Ad5 employs
several features to selectively and individually target these
isoforms, by relocalization of Sp100B/C/HMG from PML-NBs
prior to association with viral replication centers. In contrast,
Sp100A is kept at the PML tracks that surround the newly
formed viral replication centers as designated sites of active
transcription. We conclude that host-restriction factors
Sp100B/C/HMG are potentially inactivated by active
displacement from these sites, whereas Sp100A is retained to
amplify Ad5 gene expression. In sum, we provide evidence
that Ad5 selectively counteracts antiviral responses, and at
the same time benefits from proviral PML-NB associated
components by actively recruiting them to PML track-like
structures.
Volker Beusmann, Markus Schorling, Susanne Stirn
FSP BIOGUM
Dem Stress durch Züchtung ein Schnippchen schlagen?
Abstract:
Durch die Züchtung stresstoleranter Pflanzen erhofft man
sich, auch unter unsicheren Bedingungen Erträge
erwirtschaften zu können, die Konflikte um die Ressource
„Land“ zu vermindern sowie die zu erwartenden Einflüsse des
Treibhauseffektes (weniger Niederschläge) auffangen zu
können. Im Bereich trockentoleranter Pflanzen wird
hauptsächlich am Mais geforscht. Hier gibt es sowohl
konventionelle Züchtungsansätze unter Nutzung
biotechnologischer Methoden (molekulare Marker) als auch
erste gentechnisch veränderte Pflanzen. Am Beispiel dreier
ausgewählter Maislinien wird aufgezeigt, welche
Forschungsfragen aus Sicht der Technikfolgenabschätzung
beim Anbau und der Nutzung dieser Pflanzen bearbeitet
werden.
Carolin Bürck
Arbeitsgruppe Virale Transformation, Heinrich-Pette Institut,
Leibniz-Institut für Experimentelle Virologie
Efficient replication of human Adenovirus type 5 (Ad5)
requires PTM of the cellular co-repressor KAP1
Abstract:
KAP1 (KRAB-associated protein 1) plays a major role in
multiple cellular processes like apoptosis, DNA repair and
gene silencing. Recruitment of KAP1 to chromatin promotes
its compaction by increasing H3K9me2/3 repressive histone
marks, thereby potentiating KAP1 interaction with HP1. KAP1
is phosphorylated in response to DNA damage and
accumulates as pKAP1-S824 to become functionally inactive
resulting in chromatin relaxation. Vice versa inhibition of
KAP1 phosphorylation prevents decondensation of
heterochromatin repair foci, which renders cells
hypersensitive to DSB inducing agents.
Recently, we reported that alteration of chromatin structure
plays a key role in efficient Ad5 replication. Here, we provide
evidence that viral phosphoprotein E1B-55K functionally
cooperates with the C-terminal part of the KAP1 host-cell
factor. We further demonstrate that KAP1 phosphorylation at
serine 824 is a crucial step for efficient viral gene expression
and progeny production. Simultaneously, we can show a
decrease in levels of SUMOylated KAP1 during Ad infection,
known to mediate chromatin-decondensation, as well as a
vice versa effect of KAP1 overexpression on the SUMOylation
status of Ad5 proteins. Based on our findings, we hypothesize
that Ad-mediated modulation of PTM (posttranslational
modifications) of KAP1 minimizes chromatin condensation
and gene silencing, thereby maintaining efficient viral gene
expression.
Anna-Lena Cory
AG Ethologie
Mating on time: Mechanisms of mate attraction in Argiope
bruennichi
Abstract:
For mate attraction, female spiders use sex pheromones
found in the web silk and/or on the female body. Pheromone
emission is dynamic and may be enhanced by virgin females
close to oviposition. However, experimental studies about
chemical mate attraction in web-building spiders are scarce.
In field experiments, we varied pheromone source and
female age and examined mate attraction measured as the
number of male visitors per female/web within two hours in
the orb-web spider Argiope bruennichi. To compare the
attraction efficiency of female bodies with that of web silk,
we put virgin females in neutral non-pheromone webs of sub-
adult conspecifics and we used webs of pheromone-
transmitting females without the females. Both types of webs
were placed into a natural population and we found that
receptive females on neutral webs attracted more males than
webs alone built by receptive females. Young, middle-aged
and old, virgin females or their webs were brought to the
field simultaneously and we found that independent of the
pheromone source; old females were more attractive than
young and middle-aged females. The results suggest that
females increase pheromone production with number of days
they remain unmated which affects silk and body.
Eva-Maria Disch
Molekulare Pflanzenphysiologie
Membrane-Associated Ubiquitin Ligases in Plant Immunity
Abstract:
Plants use different strategies and mechanisms to fight
against pathogen infections. Plant U-box armadillo repeat
(PUB-ARM) ubiquitin ligases are regulators of development,
stress responses and pathogen defense. We have previously
identified a small conserved subgroup of PUB-ARM ubiquitin
ligases that have an elongated C-terminus carrying an
additional ARM repeat domain. This domain is essential and
sufficient to associate this group of PUB-ARM proteins to the
plasma membrane. Arabidopsis saul1 mutant plants lacking
expression of the SAUL1 gene, which encodes the plasma
membrane-associated SENESCENCE-ASSOCIATED UBIQUITIN
LIGASE 1, show early cell death and auto-immune
phenotypes. These mutants are less susceptible to different
pathogens. All phenotypes can be rescued by high
temperature or by additionally knocking out the PAD4 or
EDS1 defense gene, respectively.
Hannes Gonschior
AG Warnecke
Versuche zur Biosynthese bakterieller Glycolipide in
Säugerzellen
Abstract:
Hitzeschock-Experimente mit Zellen des Schleimpilzes
Physarum polycephalum sowie mit Säugerzellen führen zu
einen schnellen Biosynthese von Steryl-Glycosiden
(Murakami-Murofushi et al., J. Biol. Chem. 1997; 272: 486-9;
Kunimoto et al., Cell Struct. Funct. 2002; 27: 157-62). Dabei
wird ein Zuckerrest auf das Membranlipid Sterol (z.B.
Cholesterol = Cholesterin) übertragen. Die biologische
Funktionen dieses neuen Glycolipids in den Zellen sind nicht
bekannt; die Steryl-Glycoside werden aber als Mediatoren der
Stress-Antwort angesehen.
Bei Pflanzen, vielen Pilzen und einigen Bakterien sind Steryl-
Glycoside normaler Bestandteil zellulärer Membranen (Grille
et al., Progr. Lipid Res. 2010; 47: 262-288). Die Gene einiger
Glycosyltransferasen, die den Zucker auf das Sterol
übertragen, wurden bereits kloniert.
In dieser Bachelorarbeit sollen Cholesterol-
Glycosyltransferasen aus den humanpathogenen Bakterien
Helicobacter pylori, Borrelia burgdorferi und Borrelia hermsii
in Säugerzellen exprimiert werden, um dort die Biosynthese
verschiedener Cholesteryl-Glycoside zu verursachen. Diese
Zellen wären für Experimente über die Hitzeschock-Reaktion
geeignet. Nach der Transfektion von CHO- und Cos-7-Zellen
mit entsprechenden Plasmiden auf Basis des pQETris-Systems
von Qiagen konnte mit Hilfe eines Enzymassays mit radioaktiv
markierten Substraten keine Cholesterol-Glycosyltransferase-
Aktivität detektiert werden.
Wing Hang Ip
Arbeitsgruppe Virale Transformation, Heinrich-Pette Institut,
Leibniz-Institut für Experimentelle Virologie
Modulation of the IKK complex during human Adenovirus
(Ad) infection
Abstract:
Human Adenovirus (Ad) infections show a high mortality rate
in patients with strongly impaired immune response due to
strong cytokine storm and uncontrolled immune responses.
Activation of pro-inflammatory cytokines is induced early
after infection by activation of the cellular NF-kB pathway.
Here, we observe a regulatory loop between Ad and cellular
factors of the NF-kB stress pathway, indicating that the
activation of NF-kB is crucial for efficient Ad replication. Our
results show that formation of the IKK complex after
stimulation of the NF-kB pathway is impaired upon Ad
infection. We also observe that Ad induces the relocalization
of the IKKα into foci surrounding the newly formed viral
replication centers, designated sites of active transcription in
the host cell nucleus. Mimicking removal of IKKα in the cell,
knock down of this cellular IKK component using RNAi
techniques resulted in significantly impaired Ad replication.
Vice versa, overexpression of IKKα increased Ad progeny
production. We conclude that IKKα is actively recruited to
sites of Ad gene expression to selectively counteract antiviral
responses, and simultanously benefit from NF-kB
constituents. Our findings provide insights into novel
strategies for manipulating transcriptional regulation, to
either inactivate, or amplify viral gene expression.
Jonas Koch
AG Burmester
Functional analysis of the vertebrate globin-repertoire in cell
culture
Abstract:
Hemoglobin (Hb) and myoglobin (Mb) have well established
functions in oxygen transport and storage. In recent years, six
additional globin types (androglobin [Adgb], neuroglobin
[Ngb], cytoglobin [Cygb], globin E [GbE], globin X [GbX] and
globin Y [GbY]) have been identified in vertebrates. The
functions of these globins are still poorly understood. In
addition to specific roles in O2 supply, several functional
hypotheses have been put forward. These include a role in
intracellular signaling, decomposition or production of nitric
oxide and the detoxifying of reactive oxygen (ROS). We
employed a strictly comparative approach in a cell culture
system. Mouse neuronal cells (HN33) were stably transfected
with zebrafish (Danio rerio) Mb, Ngb, Cygb 1 and 2, or GbX,
with mouse (Mus musculus) Mb or Ngb, or with chicken
(Gallus gallus) GbE. HN33 cells transfected with the empty
vector (pcDNA3.1+) were employed as mock-control. The
cells were kept under hypoxic conditions (1 % O2 for 6, 24
and 48 h) and ROS-stress was induced by hydrogen peroxide
(H2O2) for 24 h. Cell viability was measured via the activity of
the mitochondrial dehydrogenases and the ATP-amount of
the cells. The results suggest that all globins enhance cell
viability under hypoxia with variable efficiency and that GbX
and Ngb most efficiently protect from ROS. In addition, we
measured globin-induced ROS-production, which show that
Ngb and GbE increase ROS under hypoxia and H2O2-induced
stress. These results allow evaluating different hypothesis of
globin functions.
Jennifer Lohr
AG Dobler
Biological role of triplicated Na, K-ATPase1α genes in the
large milkweed bug, with regard to target-site insensitivity
against cardiac glycosides
Abstract:
Plants produce a wide variety of secondary metabolites,
including alkaloids, terpenoids and glycosides, many of which
serve as antiherbivore or antimicrobial defense compounds.
In response, a substantial number of insect species have
evolved adaptations specific to the particular defensive
compounds of their host plants. The large milkweed bug,
Oncopeltus fasciatus feeds on cardiac glycoside containing
plants, and as a result must cope with the blocking of its Na,
K-ATPase´s. As an adaptation to counter the toxic effects of
these cardiac glycosides, milkweed bugs contain three copies
of the Na, K-ATPα subunit coding gene (copies A-C).
Molecular docking simulations, as well as genetically
engineered Na, K-ATPase constructs, suggest that the three
copies differ greatly in their sensitivity to cardiac glycosides.
Moreover, a preliminary gene-expression study indicates that
the two putatively less sensitive copies (A and B) are
expressed in the gut where the cardinolides are processed,
whereas the putatively more sensitive copy (copy C) is
localized to the brain, where the glial sheath likely acts as a
barrier against cardenolides. The goal of our research is to
systematically categorize the function and expression
patterns of these gene copies using RNAi. An advantage of
the insect system is that dsRNA can be injecting into adults
(or in fact any life stage), after which screens can be run
immediately for phenotypic changes. Our approach will be to
knock out each copy of the ATP1α gene and look for
differences in the expression of the other gene copies qPCR.
Rainer Neumann
AG Verhaltensbiologie
Comparative assessment of adaptive developmental
plasticity in African golden-silk spiders: males in Nephila
senegalensis (but not in N. fenestrata) accelerate sexual
maturation in response to female silk cues
Abstract:
Phenotypic plasticity allows animals to deal with
environmental uncertainty, but plasticity may also bear
fitness costs. In male spiders, female silk cues have been
proposed to induce plastic adjustment of maturation to
female availability. In general, males should accelerate
development in response to female cues. Nephila
senegalensis and N. fenestrata are closely related, but differ
considerably in size, developmental durations, and ecology.
N. senegalensis occurs in more variable habitats and female
availability should be less predictable in this species. Based on
these assumptions, we expected stronger plastic responses in
N. senegalensis males compared to N. fenestrata males. We
reared spiders under standardized conditions in climate-
control chambers. Spiders in the ‘Female cues treatment’
were regularly presented with virgin females´ silk, while
spiders in the ‘No cues treatment’ were reared in the absence
of such cues. We recorded the duration of male development
until reaching maturity. Males in N. senegalensis matured
several days earlier when presented with female silk cues,
which could entail significant benefits under natural
conditions. N. fenestrata males showed no response to
female cues at all. We suggest that males in this species are
able to rely on abiotic cues due to less variable female
presence in natural populations.
Janina Rahlff
AG Biologische Ozeanographie
Cellular and physiological responses to heat stress in neritic
copepods
Abstract:
A better understanding and ability to measure
environmental-induced stress is of growing importance given
ongoing, climate-driven changes in marine habitats.
Poikilothermic invertebrates inhabiting coastal areas and
estuaries are particularly appropriate model organisms for
studying the effects of stress since they are naturally exposed
to environmental fluctuations in key abiotic factors such as
temperature or salinity. This study examined the effect of
heat stress on Acartia tonsa and Eurytemora affinis, two
nertic copepods by quantifying the biochemical (expression of
heat shock proteins Grp78, Hsp70, Hsp90) and organismal (O2
consumption rates) responses. A second objective was to
examine the role of acclimation to warmer conditions on
biochemically responses to heat stress. Increasing
temperature caused increased amounts of Hsp transcripts
and increased respiration rates. Accumulating protein
quantities over time could be detected. Acclimation to
warmer temperature significantly decreased the heat stress
response leading to lower Hsp levels compared to non-
acclimated individuals. The temperature-associated plasticity
for the activation of heat shock proteins in copepods together
with their sustainable efficacy and efficiency during cellular
protection may explain why this protein family is evolutionary
so well-conserved among eukaryotes.
Sabrina Schreiner
Arbeitsgruppe Virale Transformation, Heinrich-Pette Institut,
Leibniz-Institut für Experimentelle Virologie
Viral oncoprotein E1B-55K binding to specific PML isoforms
is essential for efficient transformation of primary rodent
cells
Abstract:
E1B-55K from adenovirus type 5 (Ad5) is an antiapoptotic
protein and contributes in vitro to complete cell
transformation of primary rodent cells. Inhibition of p53-
activated transcription plays a key role in processes by which
E1B-55K executes its oncogenic potential. Additional
functions of E1B-55K or protein interactions with cellular
factors, such as Daxx (death-associated protein) including
SUMO posttranslational modification and integrity of nuclear
multiprotein complexes (PML-NBs) may also contribute to the
transformation process. However, the biochemical
consequences of PML-associated E1B-55K by SUMO
conjugation have so far remained elusive. We performed
mutational analysis to define a PML interaction motif within
the E1B-55K polypeptide. These studies showed that E1B-
55K/PML binding is not required for p53 and Daxx interaction;
but illustrates a prerequisite for efficient E1B-55K SUMO
conjugation. Additionally we observed that E1B-55K lacking
PML-IV or PML-V binding was no longer capable of E1B-55K-
dependent SUMOylation of p53. Surprisingly, these E1B-55K
mutants also lost the ability to inhibit p53 mediated
transactivation and showed reduced transforming potential in
primary rodent cells. These results together with the
observation that p53 SUMOylation is required for efficient
cell transformation, provides evidence that the SUMO ligase
activity of the viral oncoprotein is intimately linked to its
growth promoting oncogenic activities.
Kim Schwarze
AG Burmester
Globins in a turtle's shell: The globin repertoire of the
Chinese softshell turtle (Pelodiscus sinensis) and the western
painted turtle (Chrysemis picta bellii)
Abstract:
Globins are small heme-containing proteins that reversibly
bind oxygen and thus play an important role in respiration,
but may also have other functions. Globins offer a unique
opportunity to study the functional evolution of genes and
proteins. We have characterized the globin repertoire of two
different turtle species: the hypoxia-sensitive Chinese
softshell turtle (Pelodiscus sinensis) and the anoxia-tolerant
western painted turtle (Chrysemis picta bellii). In the genomes
of each species, we have identified eight distinct globin types.
Therefore, along with the coelacanth, turtles appear to be the
only vertebrates with a full globin repertoire. Phylogenetic
analyses revealed an early divergence of distinct globin types
and a closer relationship of myoglobin and globin E on the
one hand, and hemoglobin and globin Y on the other.
Quantitative real-time RT-PCR experiments reveal that most
of the turtle's globins are expressed in a tissue-specific
manner. Like in birds, expression and localization of the
globin E protein in the turtles is restricted to the eye, in the
pigment epithelium. Globin E may either play a myoglobin-
like role in oxygen supply in the metabolically active cells or
have functions in detoxification of reactive oxygen species.
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